This invention relates to the treatment of effluent gases produced during the manufacturing of semiconductor devices and, more specifically, to the treatment of water used in the abatement of toxic constituents of effluent gases produced from chemical vapor deposition fabrication steps in the manufacture of semiconductor devices.
The manufacture of semiconductor devices produces a variety of waste products including some products, which in some concentrations, may be considered as toxic. For example, chemical vapor deposition (CVD) processes may produce toxic effluent gases. During the CVD process, a carrier gas transports gaseous reactants into a reaction chamber in which a semiconductor device is supported. The reactants impinge on the semiconductor device surface and may undergo chemical reactions forming desired films on the device surface. Gaseous by-products, or effluent gases produced by such reactions are exhausted from the reaction chamber with the carrier gas.
The effluent gases are treated to remove any toxic gases, or to reduce the concentration of such toxic gases to acceptable levels. One form of a system for treating gases is shown in FIG. 1 as an abatement system 17 and includes a dry filter system 12 that abates the toxic gases through passive dry bed chemisorption. An exemplary filter system is manufactured by CS Clean Systems under their model designation CS125DC. In the system of FIG. 1, reactants are introduced into a CVD reactor 10 in which chemical reactions take place to form films on a semiconductor device. The carrier and effluent gases are exhausted from the reactor 10 through an outtake line 14 to a pump 11. The gases are then directed to the dry filter system 12 where the gases are treated and exhausted via line 16 into the environment with any toxic waste gases being reduced to acceptable concentration levels.
The dry filter bed abatement system of FIG. 1 requires frequent replacement of filters to ensure effective gas treatment. Not only does this require special handling in the disposal of used filter material, but the current costs of replacement material represents a substantial investment. Further, the system generally has a finite life cycle requiring periodic capital investment for replacement.
Another method used to treat effluent gases includes passing the effluent gases through an abatement system including what is known as a xe2x80x9cburn/wetxe2x80x9d scrubber. The effluent gases are first heated in a tower, and reactants are injected into the tower in order to oxidize some of the contaminants in the effluent gases. The oxidized contaminants are then passed through a rinse column and condensed by the application of rinse water. Residual gases are exhausted into the air while the rinse water, which is directed to a central water treatment facility, draws solid particulates from the system.
Newly developed silicon germanium CVD process may produce by-products containing such wastes as arsine and germanium that create further disposal problems. When burn/wet scrubbers are used to reduce arsine and germanium concentration in the effluent discharge, the rinse water, or wastewater, used to condense the toxic compounds or constituents flows to a central water treatment facility. Thus, the central wastewater facility becomes contaminated with arsenic and germanium. The central wastewater treatment facilities are not presently equipped to treat wastewater for abatement of arsenic and germanium by-products to generally accepted concentration levels.
The present invention for an abatement system incorporates a xe2x80x9cburn/wetxe2x80x9d scrubbing unit with a localized water treatment unit. The water treatment unit preferably utilizes an ion exchange filter in order to abate the concentration levels of toxic compounds, such as arsine and germanium compounds. The term abate, as used in this disclosure, is synonymous with and is used interchangeably with the term reduced.
A semiconductor device manufacturing facility typically utilizes a plurality of CVD reactors that produce effluent gases. In addition, other fabrication steps, such as plasma etching, oxidation, sputtering and reactive ion etching, may also produce undesirable effluents throughout the manufacturing facility. A wet/burn scrubber may be disposed between each of the CVD reaction chambers or other effluent gas sources and the central wastewater facility of the plant.
Effluent gas produced from the semiconductor device fabrication step is directed to the burn/wet scrubber. Some of the waste compounds are oxidized during a heating phase in the burn/wet scrubber. The oxidized compounds are condensed and separated from residual gases, which are exhausted into the air.
Water, referred to as rinse water or wastewater, used in the burn/wet scrubber to condense effluent gases, carries condensed toxic gases through the ion exchange filter, reducing undesirable constituents to acceptable concentrations. The treated wastewater is then directed to the central water treatment facility of the manufacturing plant. The use of the burn/wet scrubber avoids the cost of the dry filter systems of the prior art, and the localized treatment of the water eliminates contamination of the central wastewater treatment facility.